1. Field of the Invention
This invention concerns a liquid crystalline compound for use in liquid crystal devices and, particularly, it relates to a novel optically rotating (chiral) substance inducing the twisting arrangement in liquid crystals.
2. Description of the Prior Art
As the operation principle for the liquid crystal display device, a twisting nematic (TN) system using a nematic liquid crystal phase, a phase transition system using a cholesteric liquid crystal phase, etc have been known. In any of these systems, a liquid crystal mixture incorporated with a chiral substance has been used with an aim of inducing the twisting arrangement in the liquid crystals. Further, an attention has been attracted to a high speed light switching device by using smectic liquid crystals, particularly, smetic C* (SmC*) liquid crystal phase characterized in the twisting arrangement and utilizing the ferroelectric property thereof in recent years. In this device, an ScC* liquid crystal compound which is the chiral substance or a SmC* liquid crystal mixture incorporated with a chiral substance is used.
In this way, a chiral substance inducing the twisting arrangement is extremely important for the liquid crystal display device or the like. However, the chiral substance for use in the liquid crystal display device or the like has been required not only to have a property of optical rotation but also it is important therefor that the substance itself has a liquid crystal property or that such property is not significantly reduced when it is added to a liquid crystal mixture. Further, it is desired that the compound has a great optical rotation attributable to the induction of the twisting arrangement. That is, the following requirements (1) and (2) are considered desirable as the properties of the chiral substance:
(1) The chiral substance has a liquid crystal property or does not significantly reduce the liquid crystal property of a liquid crystal mixture when the substance is added to the mixture.
(2) The substance has a high optical rotation.
However, there have been not so many kinds of chiral substance that can sufficiently satisfy the foregoing requirements.